Numerous industrial chemicals cause pulmonary sensitivity in exposed workers. Sensitivity reactions may occur either immediately following exposure or have a delayed onset and occur several hours following exposure. An animal model demonstrating both types of respiratory tract hypersensitivity is being developed using guinea pigs. Animals will be sensitized to industrial chemicals by repeated inhalation of chemical vapors. Sensitivity is assessed by bronchial provocation challenge using low concentrations of the sensitizing allergens. Continued measurement of respiratory rates and tidal volume of guinea pigs for periods up to 48 hours following challenge, will indicate the presence of bronchial hypersensitivity. This procedure has been recently found successful for producing immediate type sensitivity to toluene diisocyanate. Using the animal model, the allergenic potencies of various industrial chemicals can be evaluated in the guinea pig and compared to their reported potencies in man. Finding a "no-response" level for guinea pigs should enable setting TLV for workers to protect against industrial sensitization. Development of chemical hypersensitivity in the respiratory tract is accompanied by other immunologic responses. These responses include specific antibody production and contact sensitivity. Recognition and measurement of these responses may allow development of tests to indicate developing hypersensitivity. Application of such tests for routine screening of industrial workers may signal early development of sensitivity and prevent occurrence of severe asthmatic reactions.